Niels Bohr once said, "Those who are not shocked when they first come across quantum theory cannot possibly have understood it.” Bohr would be right, because the very nature of quantum physics includes light somehow existing as a particle and a wave at the same time.
Consider a photon (basically a packet of light energy) that is part of a larger stream of photons (which I shall refer to as light). This photon was initially believed to be a wave, as light exhibited characteristics that were of a wave. It passed through glass, diffracted (i.e, spread out) when passed through a tiny slit, and could jump from one glass block to another if the glass blocks were close enough. However, Albert Einstein and Max Planck later conducted an experiment involving light hitting metal and ejecting electrons from it called photoelectrons. This was called the photoelectric effect.
However, they hit upon something strange. When they increased the brightness (or amplitude) of the light and attempted the experiment once more, the number of photoelectrons issued remained the same. The energy of a wave depends on its amplitude, so why couldn't it eject more photoelectrons? This was when Einstein and Planck tried to think of light as a particle, not a wave; they realized that when the photoelectric effect occurred, light was transferring some of its energy to the electrons, causing their ejection. The trouble was, light couldn't have done that unless it was a particle.
Thus, Einstein and Planck postulated that light was in fact a stream of particles called photons, with each photon essentially being a packet of energy, or a wave.
Confused? Understandable. After all, it is intuitively impossible to believe that light can exist as both a particle and a wave. Why do you think Bohr said what he said?
However, notice something interesting. When a beam of light is aimed at a very narrow angle against a block, it is trapped inside said block (this phenomenon is called total internal reflection). However, when another glass block is put very near to the first one, a part of the beam passes through that block, somehow bypassing the barrier of air between the glass blocks. One might just put that down to the wave nature of the photons, and they would be right, but many other like phenomena occur in the field of quantum physics.
One example is alpha particles being ejected from a radioactively decaying mass, despite not having the requisite velocity to do so. Another one is an electron bypassing an electric field, which requires massive energy that the electron simply doesn't have. This is explained by the wave and particle nature of subatomic particles, because, going by that theory, there is a very slight possibility that subatomic particles can be found on the other side of a barrier. This is called quantum tunnelling.
Consider a photon (basically a packet of light energy) that is part of a larger stream of photons (which I shall refer to as light). This photon was initially believed to be a wave, as light exhibited characteristics that were of a wave. It passed through glass, diffracted (i.e, spread out) when passed through a tiny slit, and could jump from one glass block to another if the glass blocks were close enough. However, Albert Einstein and Max Planck later conducted an experiment involving light hitting metal and ejecting electrons from it called photoelectrons. This was called the photoelectric effect.
However, they hit upon something strange. When they increased the brightness (or amplitude) of the light and attempted the experiment once more, the number of photoelectrons issued remained the same. The energy of a wave depends on its amplitude, so why couldn't it eject more photoelectrons? This was when Einstein and Planck tried to think of light as a particle, not a wave; they realized that when the photoelectric effect occurred, light was transferring some of its energy to the electrons, causing their ejection. The trouble was, light couldn't have done that unless it was a particle.
Thus, Einstein and Planck postulated that light was in fact a stream of particles called photons, with each photon essentially being a packet of energy, or a wave.
Confused? Understandable. After all, it is intuitively impossible to believe that light can exist as both a particle and a wave. Why do you think Bohr said what he said?
However, notice something interesting. When a beam of light is aimed at a very narrow angle against a block, it is trapped inside said block (this phenomenon is called total internal reflection). However, when another glass block is put very near to the first one, a part of the beam passes through that block, somehow bypassing the barrier of air between the glass blocks. One might just put that down to the wave nature of the photons, and they would be right, but many other like phenomena occur in the field of quantum physics.
One example is alpha particles being ejected from a radioactively decaying mass, despite not having the requisite velocity to do so. Another one is an electron bypassing an electric field, which requires massive energy that the electron simply doesn't have. This is explained by the wave and particle nature of subatomic particles, because, going by that theory, there is a very slight possibility that subatomic particles can be found on the other side of a barrier. This is called quantum tunnelling.
To further try and establish this theory, Werner Heisenberg (no Breaking Bad references please!) proposed the uncertainty principle, which states that the probability of establishing the velocity AND the position of a subatomic particle is less than Planck's constant divided by 4(pi). This uncertainty principle thus states that if you've pinned the position of a subatomic particle exactly, you can't calculate its velocity, and vice versa.
This actually explains not just tunnelling, but a lot of other concepts in quantum physics. It explains why an atom doesn't collapse (as the nucleus of an atom is composed of positively charged photons, and it is surrounded by negatively charged electrons, the electrons should be attracted to the nucleus, which would collapse the atom. This doesn't happen due to the uncertainty principle; if we can say that the electron is very near the nucleus due to the attraction, we would be determining its position, which would result in a velocity that is incalculably high; enough to stop the atom from collapsing). It also explains the radioactive decay question; if we can say that an alpha particle is in the nucleus, we are determining its position, giving it enough of a velocity to be ejected. In a way, the Heisenberg uncertainty principle exists to protect the quantum theory; many postulates made in its name would not be possible without the principle.
Quantum physics has caused us to reformulate even the most basic laws in classical physics, including the law of conservation of energy (but they still hold true!), which is one of the reasons why it is so baffling. However, it is the closest we have come to understanding the subatomic realm, so the best course of action would be to keep soldiering on in the name of this theory and try and understand the world around us on its terms.
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